Java 21 as default version

Both AEM as a Cloud Service and AEM 6.5 LTS are compatible with Java 21, and it is recommended that AEM practitioners use them. Therefore, the Archetype should use Java 21 as the default version.

Also, please note that the uber-jar of AEM 6.5 LTS (uber-jar-6.6.0) requires an API classifier like below

com.adobe.aem
uber-jar
6.6.0
**apis**
provided

CC: @chaik @rombert

Start by locating the Maven archetype configuration that selects the default Java version and defines the AEM uber-jar dependency. Check how the Java 21 default and the `apis` classifier affect generated projects, then run the repository's existing archetype generation or verification tests if available. Done means generated projects default to Java 21 and use the required AEM 6.5 LTS dependency form.

Written by the indexing model from the issue text.